


Ag and Au

by withtheworms



Category: Undertale (Video Game)
Genre: Ag and Au au, Drunk Skeletons, Implied Blowjobs, M/M, Sans Has Issues, Underfell Sans (Undertale), kustard but meaner, with friends like these who needs dentists
Language: English
Status: In-Progress
Published: 2020-03-19
Updated: 2020-09-01
Packaged: 2021-02-28 17:40:37
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 2,367
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23221111
Author URL: https://archiveofourown.org/users/withtheworms/pseuds/withtheworms
Summary: Ag and Au.  Or: Silver and Gold.Sans and Red meet by accident when they find themselves stranded in an abandoned demo of the game.  No true pacifist, no determination, no familiar faces, no Papyrus.  No resets.  Alone together they try to find a way out of what feels like a cosmic dead end, while bitterly and angrily feeding back into one another, and uh... inevitably catching feelings.It's like Kustard but a version where Red brings out the worst in Sans.  Oh, and Sans gets a silver tooth.  That's the... that's the "silver" part.
Relationships: Sans/Sans (Undertale)
Comments: 9
Kudos: 84





	1. part 1

**Author's Note:**

> this is based off a really old au idea i had like back in 2017. idk we're in social distance times and i'm just havin' fun.

Sans woke up, and before his eyes even opened he knew that he was not alone. 

He could vaguely make out the shape in the darkness, instantly recognizable; hunched and taut at the end of his bed, with twin red points of light watching him intently. 

He tensed, and as if on cue a gravelly yet uncomfortably familiar voice spoke up out of the gloom.

“You awake?”

He was. Of course he was. It was so obvious he was that the question wasn’t worth asking. 

And yet...

“No,” he mumbled, sitting up slowly, some instinct in the back of his lizard brain telling him that it was unsafe and unwise to remain laying down in this situation. He shouldn't be defenseless. He should never be defenseless against, well…

Himself.

The other Sans grinned, the glow of his eyelights illuminating the sharp points of his jagged smile. 

“I have a present for you.”

The worst thing, Sans had learned, about living with another Sans, was that he’d never be quick enough to dodge himself. 

By the time he thought of moving, the other Sans was already on him, knee pressed to his chest as he pushed him roughly down onto the ragged mattress. 

Sans thrashed to no avail as the other Sans wedged his mouth open, locking his phalanges between where his mandible connected to his skull as his other hand wrestled something into his mouth. 

He’d died so many times, it was weird to think that maybe this was it. A calm curiosity, like a bubble clinging to the filmy surface of his panic, wondered what would happen if he died in this world. They hadn’t had time to test it, too busy brooding and scraping the edge of the demo for a weakness- any sort of fissure that would allow them to claw their way out of the oubilet of a timeline they’d found themselves in. 

If resets didn’t work, here. If it was all one terribly finite dead end…… 

“ _Stop struggling_.” 

The other Sans was firm as he wrestled to keep Sans pinned down. Aggressive. 

Something deep within Sans responded to that in a way he wasn’t yet ready to unpack. 

Reluctantly he stilled, panting roughly against the fingers still jammed into his mouth. 

“There’s a good boy.”

The other Sans smiled, lascivious and razor sharp, not hesitating as he manhandled whatever he’d shoved into Sans’s mouth. There was a brief, agonizing pressure in his upper jaw, followed by a sharp burst of magic, and then the other Sans was leaning back, smug as he tilted Sans’s skull and admired his handiwork. 

“There ya go.”

Without thinking Sans shrank back and clutched a hand to his jaw, cradling the throbbing pain that radiated from the socket where his right canine used to be. The space had been numb since the other Sans punched it out in their first encounter. His tongue formed on instinct, and he prodded at the space to find something there- smooth and cold. 

“What did you do?”

There was fear in his voice that Sans did a poor job of hiding, and the other Sans rasped out a sharp bark of laughter and grinned, wolf-like.

“Why don’t you go see for yourself?”

-

The bathroom wasn’t yet dirty, but Sans could tell at a glance that it was going to get there sooner rather than later. Two Sanses, untethered from a Papyrus, with no one to deep clean the grout every sixth day and gently remind them that it was a _shared_ responsibility to pick up after themselves... It didn’t take a genius to predict that soon the pile of towels and unscrubbed grime was going to become a problem. 

A future Sans’s problem, anyway. 

His current problem was staring back at him in the mirror. His ragged reflection, the circles under his eyes darker and larger than he’d ever seen, his smile forced and painful and… 

Silver. 

He touched it with a finger. It ached, but the pain was already starting to go down. 

A silver canine, wedged into the place where his tooth had been before the Other Sans knocked it out. 

Silver, like an echo to his gold. 

Silver. 

“Do ya like it?” The other Sans slurred his words in a slow drawl, looking gleeful as he leaned against the door. “Y’see? Like mine. Matching.”

 _Matching_.

Something inside Sans, a little rotten but still incredibly pleased with itself, flared up at that word. 

“I don’t think I asked for this.”

“I don’t think you asked for me to punch it out in the first place, but I’m a generous guy.” The other Sans winked. “I learned it from being you.”

Being literally the same as one another was something Sans didn’t even want to think about. Not in a practical sense, not in a theoretical sense, and definitely not with a hard metal tooth now wedged into his skull. 

“Do you love it?” the other Sans pressed, leaning forward from the bathroom doorway in a way that threatened to crowd into Sans’s personal space.

“I hate it.”

“You don’t,” the other Sans replied flatly, profoundly unbothered by Sans’s rejection. “I remember how I felt when I got mine. You don’t hate it.”

Sans resented that. Resented the very implication of it. 

Resented how even as the other Sans spoke, he, for some reason, couldn’t take his eyes off his own reflection. That dull glint of silver. 

Fuck. 

“Yeah,” the other Sans grinned, fully in Sans’s space now. Crowding up behind him so that he could hang over his shoulder, admiring his handiwork in the mirror. “That’s what I thought.”


	2. chapter 2

**Summary for the Chapter:**

> Hi here's some more of this "Sans and Red get stuck in a dead demo of the game that they can't escape from and set about bringing out the worst in each other in an escalating feedback loop of bad coping mechanisms" AU idea. 
> 
> There's no overarching plot here, just some scenes vaguely threaded together for fun. In this one: Sans and Other Sans get drunk and dwell on how their names are the same and someone should probably get a nickname maybe. It goes nowhere and then some idiot gets his dick out.

“We need to do something about our names.”

They were sitting side by side at the bar, rewarding themselves after a busy day doing fuck all. Grillby’s was crowded with its usual regulars, the scene so similar to their home universes and yet off just enough that neither of them felt entirely comfortable. They’d been drinking- not too much, but enough that Sans felt confident bringing up the subject.

The other Sans tensed his shoulders as he glanced in Sans’s direction, his eyelights sharp.

“What about our names?”

Sans did his best to feign casual, loosely shrugging his shoulder as he lifted his glass to his mouth. 

“They’re the same.”

“Ok.”

“It’s a little awkward. Sans and Sans.”

“Ok.”

Is this what it was like for others to talk to him when he had his guard up? Christ, he was insufferable. 

Sans steeled himself, placing his glass back on the lacquered bar top. 

“I’ve been thinking of you as OS.”

"Operating System?”

"Other Sans.”

The other Sans’s grin widened immediately, his sharpened teeth on prominent display as he took clear delight in what Sans had just said. 

"Holy shit, that’s awful. Was that the best you could come up with? Seriously?”

He leaned back on his stool, laughing meanly. 

“Hey, Grillby.” With glee he waved a hand to catch the bartender’s attention, pointing first to Sans and then himself. “Check this out: He’s Sans. And I’m _Other_ Sans.”

Grillby wordlessly looked between them, making it clear he wasn’t as entertained by their hijinks as the other bar patrons tended to be. 

“... I’m busy, Sanses.”

The other Sans cackled, smacking a hand on the bar top.

"Good one, Grillbz.”

There was a flickering burst in Grillby’s flames, something subtle that he only did when he was pleased. Sans felt a weird sting twist in his gut but tried not to show it. It was stupid to think Grillby would like the other Sans more than him. It was stupid to get jealous about that. This wasn’t _his_ Grillby, anyway. 

This whole thing was stupid and he felt stupid for trying.

"It was just a suggestion.”

The other Sans quieted down, though his vicious grin remained, wolfish and ready to pounce.

"Well, it was a bad one.” He let the words hang for a moment, then looked at Sans pointedly. “Don’t call me Other Sans.”

"Ok.”

***

The snow crunched underfoot as they stumbled back towards the house; dark and cold and devoid of Papyrus. It was old snow- it hadn’t snowed in awhile. Somewhere normal that would mean spring was on its way. Not for them, though. Nothing changed, here. The old snow was endless. They’d be stumbling home treading old snow underfoot forever. 

"Sansy.”

The name burst out of the other Sans, slightly slurred but laced with intent.

"No.”

"Blue. Baby Blue. Bluebell.”

"No, no, and no.”

They’d been exchanging name suggestions ever since the original sting of the other Sans’s jeers had worn off. It had graduated to all-out name calling as the evening wore on, their voices loud and raucous over the din of the bar. Eventually Grillby had grown tired of it and told them it was time to go. At that, the other Sans had thrown his arm around Sans and they’d laughed and called _him_ names until Grillby had threatened to come around the bar and remove them himself. 

Now they were walking together, two drunk skeletons shoulder to shoulder as they did their best to stay upright and shamble the short distance back from Grillby’s. 

"This was easier when Paps came to carry me home,” Sans said suddenly, the sentence out of his mouth before he could properly think it through. 

The other Sans snickered, digging a knuckle into Sans’s ribs and making him hiss as he flinched away. 

"Shut up about your brother. I don’t care about your brother.”

Sans frowned and rubbed his side as he bit back a reply, some part of him knowing the other Sans’s intervention on this train of thought was for the best.

"Silver.”

Sans piqued, glancing at the other Sans, who grinned in response and tapped a phalange against his own golden tooth before pointing to Sans’s. 

"And Gold?”

"What? No. Fuck no,” the other Sans laughed, waving a hand dismissively. “I’m still Sans.”

"That’s not fair.”

"Look who was pitching to call me fuckin’ Other Sans.”

He had a point. 

Sans let the name run around the inside of his skull. 

"Silver.”

"Mm," the other Sans murmured, low and heady as he paused, turning so that they were looking directly at one another. "I like the way it sounds coming out of your mouth.” His attention was fixed on the silver tooth displayed prominently in Sans’s smile, and Sans could feel the hunger radiating off of him. 

It was drunk energy. This was dangerous. Neither of them should be doing this.

"Got a silver tongue,” Sans mumbled, ignoring the depth of what he was wading out into as something uncurled within him, strange and wanting. 

"Don’t I know it.”

This was unhealthy, somehow. Sober Sans could have put his finger on it, but This Many Drinks Deep Sans couldn’t pinpoint the problem exactly. All evening they’d been inching closer to one another, and all day they’d been each other’s shadows, the pattern repeating for weeks and weeks as they'd become more and more enmeshed. Inseparable. 

They shouldn't be doing this. It was something they wouldn't be able to take back if they committed to it. 

Standing on the steps leading up to their front door, with the other Sans so close Sans could feel the prickle of his magic’s aura against his bones as he idly twisted a hand into material of San’s hoodie, anchoring him in place...

The was weird.

_He wanted this._

"Kiss me.”

It was a suggestion and a direction and Sans fell into it easily, leaning forward as he pressed against the other Sans, kissing him eagerly, openly. 

For a moment the other Sans didn’t respond, and then Sans felt him instinctively tense. In an instant his easy obedience made him feel so _stupid_. Of course the other Sans hadn't meant it. Of course it had been a joke. Of course he was meant to laugh it off and go inside and then probably go throw up because now that he thought about it, he had had _way_ too much to drink.

He was already forming an excuse as he began to pull away when all at once the other Sans was kissing him back. Deeply. Hungrily. Easily, Sans folded into his taste and his touch, parting his teeth just enough that the other Sans could feel the opportunity, and then his tongue was deep in Sans’s mouth and Sans was full of him, tasting him, overwhelmed by him and-

He moaned.

They froze and Sans’s eyes snapped open to find the other Sans looking at him intently. He was sizing him up, and Sans knew, he just _knew_ , he was about to be ripped apart for that shred of stupid vulnerability. 

He was such a fucking idiot. 

This was so stupid. 

He hated himself.

He deserved what was coming.

"Heh.”

The other Sans’s hand remained on Sans’s shoulder, and his gentle squeeze pulled Sans back from the spiral he’d all too easily slipped into.

"You like that, eh?”

Sans felt the heat collecting in his face, no longer able to meet the other Sans’s eyes. 

"I don’t know.” There was no point in lying, really. There was no way he could bluff his way out of this one. “I think so."

"Yeah.” The other Sans’s voice was raw. Ravenous. “Me too.”

Sans felt himself teetering. There was something taking shape between them- fragile and ready to malform if they weren’t careful. The other Sans was so _much_. In every way succeeding where Sans saw himself a failure- brash and emotive, confident, angry, and viciously funny. A mirror of himself, but one where every failure he’d made had ended differently; a triumph of sharp points, who was able to stand up under the weight on his shoulders and face it for what it was, rather than constantly shrugging and shying away. 

Sans wanted that. Craved what the other Sans had so desperately. 

Longed for it. For _him_. 

"I’ve got a great idea what to do with your silver tongue…” The pressure on his shoulder increased, snapping Sans out of his own thoughts, and Sans found himself being pushed down onto his knees. 

It was all he needed, and he sank down willingly. 

**Notes for the Chapter:**

> "Are they really gonna do that outside their front door?" Like............. idk, probably.
> 
> i'm sorry this isn't pwp OTL next time.

**Author's Note:**

> stay safe, stay inside, wash your hands :)


End file.
